The present invention relates to an igniter for an internal combustion engine, intended to drive the ignition coils of the internal combustion engine.
In recent years, the use of an insulated gate bipolar transistor (IGBT), instead of a bipolar power transistor, is proposed as the switching device for driving the ignition coils of the internal combustion engine used for an automobile or the like.
Since it is of the voltage-driven type with added FET (field effect transistor) structure, IGBT has the advantages that it can be driven with a very weak current, compared with the current-driven type of bipolar power transistor, that the scale of the current limiting circuit added to protect IGBT from an overcurrent can be reduced in size, and that the IGBT itself and the current limiting circuit can be compactly formed on a single IC chip.
As disclosed in Japanese Application Patent Laid-Open Publication No. Hei-10-77940, the semiconductor chip into which the IGBT and the current limiting circuit for IGBT protection from an overcurrent are integrated for use in an internal combustion engine-use igniter (this chip is also referred to as the xe2x80x9cintelligent IGBT chipxe2x80x9d) is built into the TO-220 type of packaging unit, which is a standard package for an ignition power system, and this packaging unit is further mounted in the ignition coil unit.
(1) Since this type of ignition coil unit generates noise during ignition and the noise is induced as radio noise through power conductors, some users require in their specifications that a capacitor for minimizing radio noise be inserted between the power supply and the grounding terminal.
Up to now, the capacitor for reducing radio noise has been mounted outside the igniter casing that contains igniter driving circuits, or as disclosed in Japanese Application Patent Laid-Open Publication No. Hei-10-149934, the capacitor has been provided separately from the igniter driving circuit board in the igniter casing. In the latter case, a capacitor with lead wires has been connected (using a method such as soldering) to the frame that constitutes, among all external connection connector terminals provided in or on the igniter casing, only the grounding terminal and the power terminals for the primary and secondary currents.
(2) Also, other users specify a multi-functional igniter containing not only a current limiting function for IGBT protection from an overcurrent, but also a self-protection circuit . . . for example, a so-called xe2x80x9cself-shutoff functionxe2x80x9d for shutting off the current within the time during which the igniter driving circuits themselves will not become damaged, even if the ignition signal input time is unusually extended.
When circuits provided with these added functions (for example, a current limiting function for IGBT protection from an overcurrent, and a self-protection circuit) are to be formed using the prior art, a method has been adopted that requires forming a resistor and other circuit elements on a thick-film printed circuit board and mounting a monolithic IC, a capacitor, and other components, on the circuit board. The use of such a method increases costs since it requires the use of two semiconductor devices: an IGBT chip and a monolithic IC.
However, IGBT and a circuit having the added functions mentioned above (for example, a monolithic IC) can be mounted in integrated form on a single semiconductor chip, and this method enables the manufacture of an multifunctional intelligent-type chip.
The aforementioned self-protection circuit, however, is a so-called power supply type circuit operating by obtaining the necessary power from a battery power supply via a power resistor. If such a circuit is mounted together with IGBT on a single chip, therefore, power must be supplied to the chip (if the chip has only IGBT and a current limiting circuit and does not have a power supply type circuit, a circuit for obtaining power from the battery power supply via a power resistor will not be required since all that will be required is just to supply signals and the primary current to the chip).
Various types of noise surges are superimposed on the power lines of internal combustion engines. If a power supply type circuit is mounted together with IGBT on a single semiconductor chip, therefore, the semiconductor chip needs to be protected from such noise, and thus a capacitor, a resistor, and other components are required. That is to say, if these circuit protectors such as a capacitor and a resistor are mounted on the semiconductor chip, the chip size will be very large.
A radio noise reduction or surge absorption capacitor, in particular, requires a capacity of 10,000 pF or more. Even if, in an attempt to form a capacitor on a semiconductor chip, only a capacitor is formed on a chip as small as 5 mm square, a capacity not more than several thousands of picofarads can only be obtained. It is very costly and not realistic for a capacitor, a resistor, and/or other power circuit protectors to be mounted on a semiconductor device whose cost is almost proportionated to the chip size.
(3) It is also required that an electronic circuit with other electronic components be built into an igniter to realize an ignition coil unit with added functions. It takes a higher ignition coil assembly cost to independently mount electronic components, an electronic unit using the circuit board on which the electronic components are mounted, and igniter driving circuits, in or on the ignition coil unit.
The objective of the present invention is to supply an internal combustion engine-use igniter that: solves the various problems described above, is compact and excellent in mountability, and can contribute to the simplification and automation of assembly and reduce costs.
The basic configuration of the present invention for achieving the above mentioned objective is described below.
(1) One igniter is proposed, wherein: IGBT is used as the switching device for an ignition coil unit designed for an internal combustion engine, said IGBT and a current limiting circuit for IGBT protection from an overcurrent are formed on a single semiconductor chip, and this semiconductor chip (a so-called xe2x80x9cintelligent-type chipxe2x80x9d) and a capacitor for reducing radio noise are contained in a single packaging unit having external input and output terminals.
The packaging unit mentioned above is a transfer molding made of, for example, epoxy resin.
(2) Another igniter is proposed, wherein: said IGBT, a current limiting circuit for IGBT protection from an overcurrent, and a power supply type circuit are integrated on a single semiconductor chip, except for the power resistor of the power supply type circuit, and this semiconductor chip, the power resistor, and a radio noise reduction/surge absorption capacitor are contained in a single packaging unit having external input and output terminals.
(3) Still another igniter is proposed, wherein, as with the above-described igniter: said IGBT and a current limiting circuit for IGBT protection from an overcurrent are integrated on a single semiconductor chip, and this semiconductor chip and a Zener diode for the confirmation of engine control unit connection are contained in a single packaging unit having external input and output terminals.
The actions and effects of the igniters proposed above are detailed in the following description of embodiments: